range

Generates an ascending or descending numeric range that excludes its end.

Code

range.ts

/** Generates numbers from start toward end, excluding end. */
export const range = (start: number, end: number, step?: number): number[] => {
  if (!Number.isFinite(start) || !Number.isFinite(end)) {
    throw new RangeError("start and end must be finite numbers");
  }
  const direction = end >= start ? 1 : -1;
  const resolvedStep = step ?? direction;
  if (!Number.isFinite(resolvedStep) || resolvedStep === 0) {
    throw new RangeError("step must be a finite non-zero number");
  }
  if (Math.sign(resolvedStep) !== direction && start !== end) {
    throw new RangeError("step must move from start toward end");
  }

  const length = Math.ceil((end - start) / resolvedStep);
  if (!Number.isSafeInteger(length) || length > 10_000_000) {
    throw new RangeError("range would contain too many values");
  }
  return Array.from({ length }, (_, index) => start + index * resolvedStep);
};

Download

wget

Terminal

wget -O src/lib/range.ts https://raw.githubusercontent.com/jrTilak/lazykit/HEAD/registry/functions/range.ts

degit

Terminal

temp_dir="$(mktemp -d)" && bunx degit jrTilak/lazykit/registry/functions "$temp_dir" && mv "$temp_dir/range.ts" src/lib/range.ts && rm -r "$temp_dir"

Examples

range.example.ts

import { range } from "./range";

const pages = range(1, 5);
// [1, 2, 3, 4]

Props

• start (number) — Included boundary.
• end (number) — Excluded boundary.
• step (number) — Optional non-zero step pointing toward end.